Prep your pan: Preheat your oven to 400°F. Line a muffin tray with muffin liners or muffin cups, and lightly spray with non-stick spray. Cream the butter and sugar: In a large bowl or stand mixer, beat the butter and sugar together on medium speed until creamy.
Add the wet ingredients: Beat in the egg, mashed bananas, and vanilla extract until smooth. Stir in the baking soda-water mixture and a small spoon of Greek yogurt or sour cream for extra moisture.
Combine dry ingredients: In a separate bowl, whisk together the flour, nutmeg, and salt.
Mix it all together: Gradually combine the dry ingredients with the banana mixture, stirring gently until just combined. Don’t overmix, or you’ll end up with dry muffins.
Add the walnuts: Fold in the chopped walnuts (and chocolate chips if using). The batter should be thick and slightly sticky.
Fill and bake: Use an ice cream scoop to divide the batter evenly among the prepared muffin tin. Fill each cup about ¾ full and sprinkle a little turbinado sugar on the top of each muffin for that bakery-style crunch. Bake: Bake in a preheated oven at 400°F for 12–15 minutes, or until golden brown and a toothpick inserted in the center comes out with moist crumbs (not wet batter).
Cool: Let the muffins cool on a wire rack for 10 minutes before serving.
